Protective thermocontrol device for electric discharge devices



y 1950 A. M. GUREWITSCH 2,516,564

PROTECTIVE THERMOCONTROL DEVICE FOR ELECTRIC DISCHARGE DEVICES Filed Dec. 17, 1949 lnventcr'. Anatole' M. fiur-ewitsch,

His Attorneg.

Patented July 25, 1950 PROTECTIVE THERMOCONTROL DEVICE FOR ELECTRIC DISCHARGE DEVICES Anatole M. Gurewitsch, Schenectady, N. Y., as-

signor to General Electric Company,

ration of New York a corpo- Application December 17, 1949, Serial No. 133,617

My invention relates to protective devices for electric discharge devices and more particularly to a control device for automatically de-energizing an electric discharge device if it becomes overheated. My invention is particularly adapted for use with electric discharge devices having an externally extending anode or an external heat conducting member in thermal contact with its anode.

In many electronic applications of electric discharge devices and particularly in high power and high frequency applications, the electric discharge devices are operating very close to their maximum wattage ratings and any slight failure or inequilibrium in the driven circuit may cause these expensive discharge devices to burn out. Where such discharge devices are employed in high power-high frequency oscillating circuits, for example, any slight change in high frequency load, such as may be produced by a slight detuning of a resonant or tank circuit, may cause an appreciable drop in anode circuit efficiency and a dangerous rise in anode temperature.

The problem of providing a suitable thermally responsive protective device for such discharge devices may be complicated by the fact that it may be undesirable that any extraneous electrical control circuits be connected to the anode of the discharge device. Such extraneous control circuits commonly shunt the high frequency impedance of the discharge device and often greatly impair its efficiency. If, for example, the discharge device is employed in an oscillator and the anode-to-cathode circuit includes a resonant load circuit, extraneous control circuits increase the resistance component of the load circuit and thus greatly reduce the quality, or "Q, of the resonant circuit.

Accordingly, a principal object of my invention is to provide a protective thermally responsive control device for electric discharge devices which does not require any control circuit connections to the device.

A further object of my invention is to provide a simple and reliable thermally responsive protective device for electric discharge devices which may be easily adjusted to provide automatic protective control action at any desired temperature.

In general my improved control device includes three cooperating units a heat conducting plate attached to the anode of a discharge device to be protected, a switching means located adjacent but out of contact with the heat conducting plate, and a separate and unattached contact member, such as a metal pellet, which is propelled from 7 Claims. 315112) the heat conducting plate through the air to actuate the adjacent switching means when the anode of the discharge device reaches a predetermined temperature level. In order to control the temperature level at which the propulsion of this contact member occurs, a control arm is secured to the conducting plate and normally restrains the contact member within the conducting plate. This control arm moves in response to temperature variations of the conducting plate; and at a predetermined and adjustable temperature level functions to release the contact member.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, together with further objects and advantages thereof can best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 is a plan view of one embodiment of my invention as employed in combination with a pair of electric discharge devices of a well known type, and illustrates my protective control device during normal operation of the electric discharge devices, Fig. 2 is a side view partly in section of one of the discharge devices of Fig. 1 with its associated control device showing the position of the contact member after control action has occurred, and Fig. 3 is a sectional view taken along line 3-3 of Fig. 2 showing the construction and manner of attachment of the conducting plate portion of my invention to the discharge device of Fig. 2.

Referring to Fig. 1, I have shown my invention in one form in conjunction with a pair of identical electric discharge devices I of a conventional external anode type. In each of the particular discharge devices illustrated, an external cylindrical anode 2 has radially extending cooling fins 3 which support a cylindrical heat radiator 4 in concentric spaced relation to the anode 2. The remainder of each discharge device I as best seen in Fig. 2, includes a base 5 which enables the device to be vertically mounted in a conventional manner within a socket 6.

The protective control device itself comprises three separate but cooperating units. The first unit, includes a heat conducting plate 1, preferably metallic, attached to the radiator 4 by any suitable means, such as a constrictable collar 8. The second unit includes a switching means located below the conducting plate 1 and indicated generally by numeral 9, while the third unit comprises a contact member In which may conveniently be a small conductive pellet or ball bearing, as illustrated. During normal operation of the electric discharge device I, the temperature of anode 2 is not excessive and contact member I!) rests within a suitable cavity II of conducting plate I which opens through the underside of the conducting plate. The cavity II may conveniently extend through plate I as illustrated in Fig. 1 to enable contact member It to be dropped into the cavity I I from above.

The switching means 9 is arranged beneath the plate I so that it will be actuated by the dropping of contact member Iii out of the heat conducting plate cavity II. The switch itself may, of course, be any one of many different well known types and is employed to de-energize the circuit of the electric discharge device in accordance with well known methods which need not be described or illustrated here. In the instant preferred embodiment of my invention I have shown the switching means 9 as comprising an inclined guiding plate I2 having a pair of guiding channels I3 formed therein leading from beneath the cavity II in each heat conducting plate I to a switch I4 located at the intersection of channels I3. The switch I i-comprises a pair of adjacent contact faces I5 and I6, respectively, which are brought into electrically conductive relation with each other by contact member IE when it moves into the base of the intersection between channels I3, as illustrated in Fig. 2. This particular arrangement of switching means enables a common switch to serve both discharge devices.

'In order to restrain the contact member It within the heat conducting plate cavity II when the discharge device I is at normal operating temperature, I provide a control arm II which is secured to plate I and extends across the mouth of cavity II. 'In the preferred construction illustrated in the drawings and best seen in Fig. 3, control arm I? extends in spiralled fashion from a supporting stud I8 which is pivotally mounted in the conducting plate "I and whose rotational position maybe adjusted by means of a set screw I9. The free end 2i! of the arm I! may be main tained in its proper initial cavity-covering position by means of a stop pin 2! extending downward from the underside'of the conducting plate I. As the stud it is rotated counterclockwise the tension of the control arm I'I upon the stop pin 2| is increased.

The control arm I! is constructed of a pair of suitable metallic strips having dissimilar temperature coefficients of expansion so that the arm tends to move away from the stop pin 28 parallel to the bottom surface of the heat conducting plate upon an increase in the temperature of the plate I. At a certain high temperature the arm will have moved sufficiently to entirely uncover cavity II and thereby to release contact member II! to fall into the guiding channel I3 below. The temperature at which the contact member will be released is, of course, a

Many different means of propelling contact member Ill from conducting plate I to switching means 9 may of course be provided but, for simplicity and economy, I prefer to employ the motivating force of gravity as described above. However, if it should be inconvenient in a particular electronic application to place the switching means beneath the conducting plate, it will be readily appreciated that the contact member ID may be placed within a suitable cavity of the conducting plate I under the mechanical tension provided by a spring or other suitable resilient means. The switching means may then be located alongside the conducting plate in line with the trajectory of the contact member. For the proper operation of my invention however, it is essential that there be no actual contact between th switching means and the conducting plate I.

It is to be understood that while I have shown a particular embodiment of my invention, many modifications can be made, and I, therefore, intend by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A protective device for an electric discharge device of the type having an external anode comprising a heat conducting plate in thermal relation with said anode, said plate having a cavity formed therein constructed to accommodate a separable contact member, switching means located adjacent said plate and electrically isolated therefrom, and a temperature responsive control arm in thermal relation with said plate and ex" tending across the mouth of said cavity, said control arm being constructed to move out of the path of said cavity in response to a predetermined temperature variation of said plate to release a separable contact member placed within said cavity to move out of said cavity to operate said switching means.

2. A protective device for an electric discharge device of the type having an external anode comprising a heat conducting plate in thermally conductive relation to said external anode, said plate having a cavity formed therein, a switching means located adjacent but out of contact with said plate, a contact member constructed to fit within said cavity, and a temperature responsive control arm in thermal relation with said plate and extending across the mouth of said cavity whereby said contact member is restrained within said cavity, said control arm being constructed to move out of the path of said cavity in response to a predetermined temperature variation of said plate to release said contact member to move out of said cavity to operate said switching means.

3. A control device for protecting an electric discharge device of the type having an external anode from overheating comprising, a heat conducting plate attachable in thermally conductive relation to said anode, a thermally responsive control arm secured to the underside of said conducting plate and constructed to move across the under-surface of said plate in response to temperature variations of said plate, a switching means located immediately below but out of contact with said plate, and an independent contact member constructed to fit within a recess of said plate immediately above said control arm, said contact member being released by the movement of said arm to fall upon and operate said switch s eans.

4. In combination an electric discharge device having an external anode, a heat conducting plate in thermally conductive relation to said external anode, said plate having a cavity formed therein, a contact member constructed to fit within said cavity, a temperature responsive control arm secured to said plate and extending across the mouth of said cavity to restrain said contact member within said cavity, said control arm being constructed to move out of the path of said cavity in response to a predetermined temperature variation of said plate to release said contact member to move out or" said cavity, a switch and guiding means located out of contact with said plate but aligned to receive said contact member for directing said contact member to strike and operate said switch.

5. In combination an electric discharge device having an external anode, a heat conducting plate secured in thermally conductive relation to said external anode, said plate having a cavity formed therein, a contact member constructed to fit with in said cavity, switching means located adjacent but out of contact with said plate, a temperature responsive control arm pivotally mounted in said plate and extending, across the mouth of said cavity to restrain said contact member within said cavity, a stop pin extending from said plate in the path of rotation of said control arm to prevent the movement of said arm in one direction beyond said cavity, said arm being constructed to move away from said stop pin in an opposite direction out of the path of said cavity in response to a variation in temperature of said plate thereby to release said contact member to move out of said cavity to strike and operate said switching means, and means to adjust the initial rotational position of said control arm to vary the initial tension of said arm against said stop pin thereby to adjust the temperature at which release of said contact member occurs.

6. In combination, an electric discharge device having an external anode, a heat conducting plate in thermally conductive relation to said anode, said plate having a cavity formed in the underside thereof, a contact member constructed to fit Within said cavity, a switching means located immediately below said cavity but out of contact with said plate, a temperature responsive control arm secured to said plate and extending across the mouth of said cavity to restrain said contact member within said cavity, said control arm being constructed to move out of the path of said cavity in response to a predetermined temperature variation of said plate to release said con tact member to fall upon and operate said switching means.

'7. In combination, an electric discharge device having an external anode, a heat conducting plate in thermally conductive relation to said anode, said plate having a cavity formed in the underside thereoi, a contact member constructed to fit within said cavity, a switching means operable to ole-energize said electric discharge device located immediately below said cavity but out of contact with said plate, a temperature responsive control arm mounted in said plate and extending across the mouth of said cavity to retain said contact member within said cavity, a stop pin extendingfrom said plate in the path of said control arm to prevent the movement of said arm in one direction beyond said cavity, said arm being constructed to move away from said stop pin in an opposite direction out of the path of said cavity in response to a variation in temperature of said plate thereby to release said contact member to fall upon and operate said switching means.

ANATOLE M. GUREWITSCH.

l lo references cited. 

